In numerous 31P NMR spectroscopic studies of tumors and transformed cell lines it has been observed that they have substantially higher concentrations of phosphospholipid metabolites such as phosphoryl choline (PCho) and phosphoryl ethanolamine (PEth) than normal tissues. While these elevations have been observed in almost every tumor examined, the details of which metabolites are affected vary depending on the tumor type, anatomical location and species. In order to understand the mechanism underlying these phenomena, we propose in this study to examine phospholipid metabolism of normal and transformed cells in a tissue culture system. By being able to control the nutritional, hormonal and growth status of cells in culture we hope to be able to dissociate the various factors affecting phospholipid metabolism and isolate from among them the specific components associated with tumorigenic transformation. One such possible component could be the reported associated of elevated PCho levels with increased production of known mitogenic lipids such as diacylglycerol and phosphatidic acid by the action of phospholipases C and D. The main methodology used in this work will be 13C NMR spectroscopy which has not yet been exploited in the study of phospholipid metabolism. This technique will be supplemented, when appropriate, by other analytical techniques such as HPLC and TLC.